[Mesa-dev] [PATCH 3/4] glsl/gs: handle gl_ClipDistance geometry input in lower_clip_distance.
Ian Romanick
idr at freedesktop.org
Fri Sep 27 14:32:21 PDT 2013
There are some bits of this patch I'm trying to understand. I think
they can be cleared up by one question below...
On 09/14/2013 01:00 PM, Paul Berry wrote:
> From: Bryan Cain <bryancain3 at gmail.com>
>
> This corresponds to the lowering of gl_ClipDistance to
> gl_ClipDistanceMESA for vertex and geometry shader outputs. Since
> this lowering pass occurs after lower_named_interface blocks, it deals
> with 2D arrays (gl_ClipDistance[vertex][clip_plane]) rather than 1D
> arrays in an interface block
> (gl_in[vertex].gl_ClipDistance[clip_plane]).
>
> v2 (Paul Berry <stereotype441 at gmail.com>): Fix indexing order for
> gl_ClipDistance input lowering. Properly lower bulk assignment of
> gl_ClipDistance inputs. Rework for GLSL 1.50 style geometry shaders.
> ---
> src/glsl/lower_clip_distance.cpp | 223 +++++++++++++++++++++++++++++----------
> 1 file changed, 165 insertions(+), 58 deletions(-)
>
> diff --git a/src/glsl/lower_clip_distance.cpp b/src/glsl/lower_clip_distance.cpp
> index d6cf944..16eaef6 100644
> --- a/src/glsl/lower_clip_distance.cpp
> +++ b/src/glsl/lower_clip_distance.cpp
> @@ -53,13 +53,16 @@
> class lower_clip_distance_visitor : public ir_rvalue_visitor {
> public:
> lower_clip_distance_visitor()
> - : progress(false), old_clip_distance_var(NULL),
> - new_clip_distance_var(NULL)
> + : progress(false), old_clip_distance_1d_var(NULL),
> + old_clip_distance_2d_var(NULL), new_clip_distance_1d_var(NULL),
> + new_clip_distance_2d_var(NULL)
> {
> }
>
> virtual ir_visitor_status visit(ir_variable *);
> void create_indices(ir_rvalue*, ir_rvalue *&, ir_rvalue *&);
> + bool is_clip_distance_vec8(ir_rvalue *ir);
> + ir_rvalue *lower_clip_distance_vec8(ir_rvalue *ir);
> virtual ir_visitor_status visit_leave(ir_assignment *);
> void visit_new_assignment(ir_assignment *ir);
> virtual ir_visitor_status visit_leave(ir_call *);
> @@ -73,12 +76,14 @@ public:
> /**
> * Pointer to the declaration of gl_ClipDistance, if found.
> */
> - ir_variable *old_clip_distance_var;
> + ir_variable *old_clip_distance_1d_var;
> + ir_variable *old_clip_distance_2d_var;
>
> /**
> * Pointer to the newly-created gl_ClipDistanceMESA variable.
> */
> - ir_variable *new_clip_distance_var;
> + ir_variable *new_clip_distance_1d_var;
> + ir_variable *new_clip_distance_2d_var;
> };
>
>
> @@ -89,30 +94,60 @@ public:
> ir_visitor_status
> lower_clip_distance_visitor::visit(ir_variable *ir)
> {
> - /* No point in looking for the declaration of gl_ClipDistance if
> - * we've already found it.
> - */
> - if (this->old_clip_distance_var)
> + if (!ir->name || strcmp(ir->name, "gl_ClipDistance") != 0)
> return visit_continue;
> + assert (ir->type->is_array());
> +
> + if (!ir->type->element_type()->is_array()) {
> + /* 1D gl_ClipDistance (used for vertex and geometry output, and fragment
> + * input).
> + */
> + if (this->old_clip_distance_1d_var)
> + return visit_continue;
>
> - if (ir->name && strcmp(ir->name, "gl_ClipDistance") == 0) {
> this->progress = true;
> - this->old_clip_distance_var = ir;
> - assert (ir->type->is_array());
> + this->old_clip_distance_1d_var = ir;
> assert (ir->type->element_type() == glsl_type::float_type);
> unsigned new_size = (ir->type->array_size() + 3) / 4;
>
> /* Clone the old var so that we inherit all of its properties */
> - this->new_clip_distance_var = ir->clone(ralloc_parent(ir), NULL);
> + this->new_clip_distance_1d_var = ir->clone(ralloc_parent(ir), NULL);
>
> /* And change the properties that we need to change */
> - this->new_clip_distance_var->name
> - = ralloc_strdup(this->new_clip_distance_var, "gl_ClipDistanceMESA");
> - this->new_clip_distance_var->type
> + this->new_clip_distance_1d_var->name
> + = ralloc_strdup(this->new_clip_distance_1d_var,
> + "gl_ClipDistanceMESA");
> + this->new_clip_distance_1d_var->type
> = glsl_type::get_array_instance(glsl_type::vec4_type, new_size);
> - this->new_clip_distance_var->max_array_access = ir->max_array_access / 4;
> + this->new_clip_distance_1d_var->max_array_access
> + = ir->max_array_access / 4;
> +
> + ir->replace_with(this->new_clip_distance_1d_var);
> + } else {
> + /* 2D gl_ClipDistance (used for geometry input). */
> + assert(ir->mode == ir_var_shader_in);
> + if (this->old_clip_distance_2d_var)
> + return visit_continue;
>
> - ir->replace_with(this->new_clip_distance_var);
> + this->progress = true;
> + this->old_clip_distance_2d_var = ir;
> + assert (ir->type->element_type()->element_type() == glsl_type::float_type);
> + unsigned new_size = (ir->type->element_type()->array_size() + 3) / 4;
> +
> + /* Clone the old var so that we inherit all of its properties */
> + this->new_clip_distance_2d_var = ir->clone(ralloc_parent(ir), NULL);
> +
> + /* And change the properties that we need to change */
> + this->new_clip_distance_2d_var->name
> + = ralloc_strdup(this->new_clip_distance_2d_var, "gl_ClipDistanceMESA");
> + this->new_clip_distance_2d_var->type = glsl_type::get_array_instance(
> + glsl_type::get_array_instance(glsl_type::vec4_type,
> + new_size),
> + ir->type->array_size());
> + this->new_clip_distance_2d_var->max_array_access
> + = ir->max_array_access / 4;
> +
> + ir->replace_with(this->new_clip_distance_2d_var);
> }
> return visit_continue;
> }
> @@ -177,39 +212,99 @@ lower_clip_distance_visitor::create_indices(ir_rvalue *old_index,
> }
>
>
> +/**
> + * Determine whether the given rvalue describes an array of 8 floats that
> + * needs to be lowered to an array of 2 vec4's; that is, determine whether it
> + * matches one of the following patterns:
> + *
> + * - gl_ClipDistance (if gl_ClipDistance is 1D)
> + * - gl_ClipDistance[i] (if gl_ClipDistance is 2D)
> + */
> +bool
> +lower_clip_distance_visitor::is_clip_distance_vec8(ir_rvalue *ir)
> +{
Is it ever possible for both of these to be taken?
> + if (this->old_clip_distance_1d_var) {
> + ir_dereference_variable *var_ref = ir->as_dereference_variable();
> + if (var_ref && var_ref->var == this->old_clip_distance_1d_var)
> + return true;
> + }
> + if (this->old_clip_distance_2d_var) {
> + ir_dereference_array *array_ref = ir->as_dereference_array();
> + if (array_ref) {
> + ir_dereference_variable *var_ref =
> + array_ref->array->as_dereference_variable();
> + if (var_ref && var_ref->var == this->old_clip_distance_2d_var)
> + return true;
> + }
> + }
> + return false;
> +}
> +
> +
> +/**
> + * If the given ir satisfies is_clip_distance_vec8(), return new ir
> + * representing its lowered equivalent. That is, map:
> + *
> + * - gl_ClipDistance => gl_ClipDistanceMESA (if gl_ClipDistance is 1D)
> + * - gl_ClipDistance[i] => gl_ClipDistanceMESA[i] (if gl_ClipDistance is 2D)
> + *
> + * Otherwise return NULL.
> + */
> +ir_rvalue *
> +lower_clip_distance_visitor::lower_clip_distance_vec8(ir_rvalue *ir)
> +{
> + if (this->old_clip_distance_1d_var) {
> + ir_dereference_variable *var_ref = ir->as_dereference_variable();
> + if (var_ref && var_ref->var == this->old_clip_distance_1d_var) {
> + return new(ralloc_parent(ir))
> + ir_dereference_variable(this->new_clip_distance_1d_var);
> + }
> + }
> + if (this->old_clip_distance_2d_var) {
> + ir_dereference_array *array_ref = ir->as_dereference_array();
> + if (array_ref) {
> + ir_dereference_variable *var_ref =
> + array_ref->array->as_dereference_variable();
> + if (var_ref && var_ref->var == this->old_clip_distance_2d_var) {
> + return new(ralloc_parent(ir))
> + ir_dereference_array(this->new_clip_distance_2d_var,
> + array_ref->array_index);
> + }
> + }
> + }
> + return NULL;
> +}
> +
> +
> void
> lower_clip_distance_visitor::handle_rvalue(ir_rvalue **rv)
> {
> - /* If the gl_ClipDistance var hasn't been declared yet, then
> - * there's no way this deref can refer to it.
> - */
> - if (!this->old_clip_distance_var || *rv == NULL)
> + if (*rv == NULL)
> return;
>
> ir_dereference_array *const array_deref = (*rv)->as_dereference_array();
> if (array_deref == NULL)
> return;
>
> - /* Replace any expression that indexes into the gl_ClipDistance array
> + /* Replace any expression that indexes one of the floats in gl_ClipDistance
> * with an expression that indexes into one of the vec4's in
> * gl_ClipDistanceMESA and accesses the appropriate component.
> */
> - ir_dereference_variable *old_var_ref =
> - array_deref->array->as_dereference_variable();
> - if (old_var_ref && old_var_ref->var == this->old_clip_distance_var) {
> + ir_rvalue *lowered_vec8 =
> + this->lower_clip_distance_vec8(array_deref->array);
> + if (lowered_vec8 != NULL) {
> this->progress = true;
> ir_rvalue *array_index;
> ir_rvalue *swizzle_index;
> this->create_indices(array_deref->array_index, array_index, swizzle_index);
> void *mem_ctx = ralloc_parent(array_deref);
>
> - ir_dereference_array *const ClipDistanceMESA_deref =
> - new(mem_ctx) ir_dereference_array(this->new_clip_distance_var,
> - array_index);
> + ir_dereference_array *const new_array_deref =
> + new(mem_ctx) ir_dereference_array(lowered_vec8, array_index);
>
> ir_expression *const expr =
> new(mem_ctx) ir_expression(ir_binop_vector_extract,
> - ClipDistanceMESA_deref,
> + new_array_deref,
> swizzle_index);
>
> *rv = expr;
> @@ -243,30 +338,34 @@ lower_clip_distance_visitor::fix_lhs(ir_assignment *ir)
> }
>
> /**
> - * Replace any assignment having gl_ClipDistance (undereferenced) as its LHS
> - * or RHS with a sequence of assignments, one for each component of the array.
> - * Each of these assignments is lowered to refer to gl_ClipDistanceMESA as
> - * appropriate.
> + * Replace any assignment having the 1D gl_ClipDistance (undereferenced) as
> + * its LHS or RHS with a sequence of assignments, one for each component of
> + * the array. Each of these assignments is lowered to refer to
> + * gl_ClipDistanceMESA as appropriate.
> + *
> + * We need to do a similar replacement for 2D gl_ClipDistance, however since
> + * it's an input, the only case we need to address is where a 1D slice of it
> + * is the entire RHS of an assignment, e.g.:
> + *
> + * foo = gl_in[i].gl_ClipDistance
> */
> ir_visitor_status
> lower_clip_distance_visitor::visit_leave(ir_assignment *ir)
> {
> - ir_dereference_variable *lhs_var = ir->lhs->as_dereference_variable();
> - ir_dereference_variable *rhs_var = ir->rhs->as_dereference_variable();
> - if ((lhs_var && lhs_var->var == this->old_clip_distance_var)
> - || (rhs_var && rhs_var->var == this->old_clip_distance_var)) {
> - /* LHS or RHS of the assignment is the entire gl_ClipDistance array.
> - * Since we are reshaping gl_ClipDistance from an array of floats to an
> - * array of vec4's, this isn't going to work as a bulk assignment
> - * anymore, so unroll it to element-by-element assignments and lower
> - * each of them.
> + if (this->is_clip_distance_vec8(ir->lhs) ||
> + this->is_clip_distance_vec8(ir->rhs)) {
> + /* LHS or RHS of the assignment is the entire 1D gl_ClipDistance array
> + * (or a 1D slice of a 2D gl_ClipDistance input array). Since we are
> + * reshaping gl_ClipDistance from an array of floats to an array of
> + * vec4's, this isn't going to work as a bulk assignment anymore, so
> + * unroll it to element-by-element assignments and lower each of them.
> *
> * Note: to unroll into element-by-element assignments, we need to make
> * clones of the LHS and RHS. This is safe because expressions and
> * l-values are side-effect free.
> */
> void *ctx = ralloc_parent(ir);
> - int array_size = this->old_clip_distance_var->type->array_size();
> + int array_size = ir->lhs->type->array_size();
> for (int i = 0; i < array_size; ++i) {
> ir_dereference_array *new_lhs = new(ctx) ir_dereference_array(
> ir->lhs->clone(ctx, NULL), new(ctx) ir_constant(i));
> @@ -326,11 +425,17 @@ lower_clip_distance_visitor::visit_new_assignment(ir_assignment *ir)
>
>
> /**
> - * If gl_ClipDistance appears as an argument in an ir_call expression, replace
> - * it with a temporary variable, and make sure the ir_call is preceded and/or
> - * followed by assignments that copy the contents of the temporary variable to
> - * and/or from gl_ClipDistance. Each of these assignments is then lowered to
> - * refer to gl_ClipDistanceMESA.
> + * If a 1D gl_ClipDistance variable appears as an argument in an ir_call
> + * expression, replace it with a temporary variable, and make sure the ir_call
> + * is preceded and/or followed by assignments that copy the contents of the
> + * temporary variable to and/or from gl_ClipDistance. Each of these
> + * assignments is then lowered to refer to gl_ClipDistanceMESA.
> + *
> + * We need to do a similar replacement for 2D gl_ClipDistance, however since
> + * it's an input, the only case we need to address is where a 1D slice of it
> + * is passed as an "in" parameter to an ir_call, e.g.:
> + *
> + * foo(gl_in[i].gl_ClipDistance)
> */
> ir_visitor_status
> lower_clip_distance_visitor::visit_leave(ir_call *ir)
> @@ -349,12 +454,12 @@ lower_clip_distance_visitor::visit_leave(ir_call *ir)
> formal_param_node = formal_param_node->next;
> actual_param_node = actual_param_node->next;
>
> - ir_dereference_variable *deref = actual_param->as_dereference_variable();
> - if (deref && deref->var == this->old_clip_distance_var) {
> - /* User is trying to pass the whole gl_ClipDistance array to a
> - * function call. Since we are reshaping gl_ClipDistance from an
> - * array of floats to an array of vec4's, this isn't going to work
> - * anymore, so use a temporary array instead.
> + if (this->is_clip_distance_vec8(actual_param)) {
> + /* User is trying to pass the whole 1D gl_ClipDistance array (or a 1D
> + * slice of a 2D gl_ClipDistance array) to a function call. Since we
> + * are reshaping gl_ClipDistance from an array of floats to an array
> + * of vec4's, this isn't going to work anymore, so use a temporary
> + * array instead.
> */
> ir_variable *temp_clip_distance = new(ctx) ir_variable(
> actual_param->type, "temp_clip_distance", ir_var_temporary);
> @@ -370,7 +475,7 @@ lower_clip_distance_visitor::visit_leave(ir_call *ir)
> */
> ir_assignment *new_assignment = new(ctx) ir_assignment(
> new(ctx) ir_dereference_variable(temp_clip_distance),
> - new(ctx) ir_dereference_variable(old_clip_distance_var));
> + actual_param->clone(ctx, NULL));
> this->base_ir->insert_before(new_assignment);
> this->visit_new_assignment(new_assignment);
> }
> @@ -382,7 +487,7 @@ lower_clip_distance_visitor::visit_leave(ir_call *ir)
> * afterwards to make sure it gets lowered.
> */
> ir_assignment *new_assignment = new(ctx) ir_assignment(
> - new(ctx) ir_dereference_variable(old_clip_distance_var),
> + actual_param->clone(ctx, NULL),
> new(ctx) ir_dereference_variable(temp_clip_distance));
> this->base_ir->insert_after(new_assignment);
> this->visit_new_assignment(new_assignment);
> @@ -401,8 +506,10 @@ lower_clip_distance(gl_shader *shader)
>
> visit_list_elements(&v, shader->ir);
>
> - if (v.new_clip_distance_var)
> - shader->symbols->add_variable(v.new_clip_distance_var);
> + if (v.new_clip_distance_1d_var)
> + shader->symbols->add_variable(v.new_clip_distance_1d_var);
> + if (v.new_clip_distance_2d_var)
> + shader->symbols->add_variable(v.new_clip_distance_2d_var);
>
> return v.progress;
> }
>
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